Section 31. There shall be paid by the commonwealth to the chairman of said board the sum of twenty-five hundred dollars annually, to the secretary of said board the sum of eighteen hundred and seventy-five dollars, and to each of the other members of said board the sum of twelve hundred and fifty dollars, and to all members of the board their necessary traveling and other expenses actually expended in attending meetings thereof. Said board may expend any sum not exceeding five hundred dollars annually for purposes of instruction and dissemination of new and useful knowledge among and for the benefit of registered embalmers and funeral directors; provided, that such salaries and expenses shall not be in excess of the receipts for registration and renewals thereof received by the state treasurer from the board.